A common problem with one-point grease distribution systems for belt conveyor idlers is that quite often the result is that too much grease is applied to the bearings closest to the entry point of the grease to the idler assembly and not enough grease is applied to the bearings farther from the point of entry of the grease.
One such system is commonly referred to as a non-purging system which has a grease fitting for receiving the grease gun or the like on one end of one of the rollers and the opposite end of the most distant roller has a relief valve thereon which will release grease therefrom only after the grease flow chamber is completely full and pressurized to the point where the pressure overcomes the preset pressure for such relief valve. It has been found, however, that quite often while the grease has clearly gone from one end of the grease supply channel to the other, the pressure is not great enough to cause sufficient amounts of grease to actually enter the bearings. This is true even though grease has exited the relief valve. This problem will tend to worsen over time as the spring for the relief valve weakens, causing the pressure in the grease supply channel to have a maximum pressure which is less than it was when the system was initially installed.
Another one-point grease distribution system for belt conveyor idlers is shown in U.S. Pat. No. 4,174,031 to MacLeod. This shows an idler roller having a hollow shaft on which the roller rotates as well as providing a channel completely through the center thereof for the grease supply channel. Orifices are provided for communicating the hollow shaft with the grease seal reservoir which is disposed on both sides of each bearing. One of the problems with such a system is that hollow shafting is expensive as compared to solid shafting. Another problem is that hollow shafting is not as strong as solid shafting. A still further problem with hollow shafting is that the hollow shaft grease passage in the connection from one idler bearing to the next, causes a restriction which slows down the flow of grease and causes the pressure of the grease to be higher in the rollers closest to the entry point of the grease and at a lower pressure the farther away the hollow shafting is from the point of entry of the grease, thereby delivering less grease to the bearings at the more remote points and applying too much grease at the bearings closest to the point of entry of the grease into the grease supply channel.
Another type of one-point grease distribution system for belt conveyors has a rotating sleeve which is exemplified by the first embodiment shown in U.S. Pat. No. 3,198,318 to Brown. While this Brown device uses a solid shaft and overcomes some of the problems with the hollow shaft, other problems are created. For example, an additional sleeve surrounds the center of the shaft in each roller and provides flow of grease between the solid shaft and the surrounding cylinder. A problem with this type of system is that the cylinder inside of the roller actually rotates with the roller, whereas the shaft itself remains stationary. This means that the grease in the grease supply chamber has walls which rotate with respect to each other. Another very serious problem with this configuration is that especially in the cold weather when the conveyors are stopped and when they are re-started, the grease in the grease supply channel stiffens. This will cause an even greater resistance of the roller to rotation due to the presence of the hard grease in the grease supply channel because the grease supply channel walls must move with respect to each other.
Consequently, there is a need for a one-point grease distribution system for belt conveyor idler rollers which overcomes the aforementioned problems.